With rapid development of display technologies, touch-screen panels have been gradually applied throughout in people's life. At present, touch-screen panels, according to their working principles, can be classified as: resistive type, capacitive type, infrared type, and surface acoustic wave type. Among them, capacitive touch-screen panels, by virtue of their unique touch principles and their advantages of high sensitivity, long life and high light transmittance, etc, have become the most favorable and pursued products in the industry.
Nowadays, in order to make a capacitive touch-screen panel thinner, a kind of capacitive in-cell touch-screen panels has appeared, in which touch electrodes are manufactured inside of its color-filter substrate; for example, on an existing TFT (Thin Film Transistor) array substrate, touch scanning lines and touch sensing lines are directly added to achieve a touch function; that is, on the surface of the TFT array substrate, two layers of strip-like ITO (Indium Tin Oxides) electrodes that are intersected each other on different levels (non-coplanar intersection) are provided, and these two layers of ITO electrodes are used as touch scanning lines and touch sensing lines of the touch-screen panel, respectively, meanwhile an inductive capacitor is formed at a non-coplanar intersection position between two ITO electrodes.
Also for example, because the touch precision of a touch-screen panel is typically on a millimeter-order, whereas the display precision of a ITT array substrate is typically on a micron-order; therefore, the required touch scanning lines and touch sensing lines for a touch screen are much less in amount than the driving lines (data lines and gate lines) required for the display function of a TFT array substrate; moreover, in a TFT array substrate, the data line and the gate line corresponding to each TFT intersect in a non-coplanar way, that is, the two lines are mutually insulated while their projections along a vertical direction intersect each other, thus part of the driving lines (data lines and gate lines) in a TFT array substrate can be used as touch lines (touch scanning lines and touch sensing lines) of a touch-screen panel, and inductive capacitors are formed at the non-coplanar intersection positions of the data lines and gate lines. so that the function of a capacitive touch-screen panel can be achieved.
The working process of the above-described two types of capacitive in-cell touch-screen panels is: when an ITO electrode acting as a touch scanning line is loaded with touch scan signals, coupled voltage signals that are obtained by a touch sensing line via an inductive capacitor are detected; and during this process, when a human body contacts the touch-screen panel, the human body electric field will act on the inductive capacitor, causing the capacitance value of the inductive capacitor to change, and further cause the coupled voltage signals obtained by the touch sensing line to change; then, according to the changes of the voltage signals, the position of the touch-point can be determined.
A touch-screen panel having a high resolution needs to be prepared by using one-chip technology, which integrates gate driver circuits in order to reduce the areas of the panel periphery circuits; thus, in the case where a gate line is also used as a touch scanning line, touch scan signals also have to be provided by the corresponding integrated gate driver circuit. For the integrated gate driver circuit, such as a GOA (Gate Driver on Array, which is an array substrate row-driver circuit), when it provides gate drive signals to gate lines, generally, at least one shift-register circuit is required for one GOA circuit to output one gate drive signal, and thus, N shift-register circuits are required for N gate lines; therefore, as external clock signals need to enter into these N shift-register circuits simultaneously, a signal-delay problem will occur; on the other hand, touch scanning lines have more stringent real-time requirements on touch scan signals, if an existing integrated gate drive circuit (e.g., GOA) is directly used to provide touch scan signals for a touch scanning line, a signal-delay problem will occur, and this will lead to the problem that a touch operation cannot be identified properly.